Method of making electrical apparatus.



S. TROOD.

- METHOD OF MAKING ELECTRICAL APPARATUS.

APPLICATION FILED JAN. 1, 1914.

1,150,081 I Patented Aug. 17, 1915.

. ATTORNEY Unrrnn srnrns SAMUEL TROOD, 0F WILKINSBUBG, PENNSYLVANIA,ASSIGNOR TU VJESTINGHOUSE ELECTRIC AND MANUFACTURING COMPANY, ACORPORATION (3F EENNSYLVANIA.

IMETHGI) OF IVZAKIHG ELECTRICAL APPARATUS.

Specification. of Letters Patent.

Fatented Aug. 1%, $915..

Application filed January 7, 1914. Serial Ito. 810,776.

new and useful Improvement in Methods of Making Electrical Apparatus, ofwhich the following is a specification.

My invention relates to methods of making electrical apparatus, and ithas special reference to electric heating devices.

The obj oct of my invention is to provide a method of making devices ofthe aboveindicated class which shall be simple and in expensive andwhich shall secure new an highly desirable features in the completedapparatus.

More specifically, the object of my invention is to provide a methodwhereby, when an incasing member is cast around a conductor, theconductor will contract at the same 'rat'e as the incasin; member duringcooling thereof, and thus the mutual thermal contact of the parts willremain as intimate as at first, and no undue stresses will occur.

Heretofore, in devices of the general class in question, the electricalconductor has not been adapted to contact with the cooling incasinp;member and. consequently, undue strains have been caused, and variousparts have undergone cracking or other weakening conditions, which alsomilitated against the maintenance of intimate thermal contact betweenthe parts.

According to my invention I embed a, suitable electrical conductor orheating element in a relatively plastic cement or other suitablematerial of good heat-conducting and electrically insulating properties,I then preferably bake the cement, and next use the combined body as acore around which a copper or other suitable metallic incasing member iscast. Prior to and during the casting operation, I pass through the conductor a current of such value that it is caused to expand an amountthat corre sponds to the expansion present in the initially solidifiedincasing' member. As the member cools and contracts, the current throughthe incloscd conductor is either cut oil or is gradually reduced inaccordance with the temperature reduction of the ineasmg member, ashereinafter described. In this manner, the conductor, the inclosingmaterial and the incasing member all cool and contract at substantiallythe same rate, thereby maintaining intimate mutual thermal contactbetween the parts, while obviating the above-mentioned diflicultiescracking and the like.

In the accompanyingdrawing, the single figure is a view, partially inlongitudinal section, and partially diagrammatic, illuscrating themethod constituting my invention.

Referring; to the drawing, the apparatus here shown comprises anelectrical conductor or heating; element 1 which is preferably wound onan insulating spool 1; an envelop 2 therefor of relatively plasticcement or other suitable material of good heat-com ductin andclectrically-insulatin ro Jerties; an incasing member 3 of copper orother suitable metallic matenal, here shown as a soldering iron tip; asuitable mold 4:

for casting the incasing member 3 around the envelop 2; supplyconductors 5 for con necting the heating element 1 to a source ofelectrical energy (not shown); a switch. 6,

and a rheostat 7 for varying the current supplied to the element 1.

Considering now the various steps of my process, the electricalconductor 1 and its spool 1* are first embedded in the relativelyplastic cement 2, which is fashioned in the 35 desired shape and size.The combined body is then baked. as is customary in the production ofcores in the molding art, and the combined body is employed as a corefor a casting; or" copper or other suitable material. 99

The core may be held in position during the casting: process in anysuitable manner, suc'i as by the threaded collar device 8 shown in thedrawing.

A predetermined time prior to the casting process. the switch 6 isclosed to send a current through the heating element 1 and the rheostat7. of such value that the element is heated and caused to expand anamount corresponding to the expansion present in 0 the initiallysolidified tip 3. An intimate thermal contact thus obtains between theand contracts the current is As the element 1 and the tip 3.

prei oli' immediately after solidification, i. conductor and the castmember are same material, and the rheostat is preferably actuated togradually include more sistance in the circuit if the two members are ofdissimilar materials, thereby in the latter case, reducing); the currenttraversing the heating element in such ratio that the change oftemperature of the element and its contraction correspond to thetemperature variation and shrinkage of the tip 3.

Thus it will be noted that in either case, the

tip. the cement and the heating element all cool and contract togetherat substantially the same rate, thereby permanently in 'n rainingintimate thermal contact between the parts.

1 do not wish to be restricted to the specilic arrangement of parts andthe struc laral details herein set forth, as modifications till-erectmay be made within the spirit and scope of my invention. It, therefore,de-

sire that only such limitations shall be imposed as are indicated in theappended claims.

.l claim my invention:

1 The method of making an electrical device that comprises applying anelectric current to a conductor during the casting oi material aroundsaid conductor and thereafter cooling the said conductor and the saidcast material in such manner that they contract at substantially thesame rate.

2. The method of making an electrical device that comprises applying anelectric current to insulated conducti'ir during the disposal of heatedi aterial around said conductor, and tlurrealter cooling the saidconductor and the said material in such .anner that they contract atsubstantially the same rate.

. 3. The method of making an electrical de vice that connirises theapplication of an electric currimt to a conductor provided withinsulating material during the casting of an incasing member around saidmaterial and during" a predetermined period of cooling after completionof the casting operation.

4. The method of" making an electrical device that comprises theapplication of an electric current to a condi'ictor during the casting:of material around said conductor. and the variation of said currentwhile said material is cooling.

5. The method of making, an electrical de-' vice that comprises theapplication of an electric current to a. conductor provided withinsulating material dining the casting cl an incasing' member aroundsaid material. and a reduction of the current in ac cordance with thetemperature reduction of said nien'iber as it cools.

The method of making; an electrical device that comprises applying anelectric current to conductor during the disposal of metallic materialaround said conductor and in good thermal contact therewith, andthereafter cooling the said conductor and the said material in suchmanner that they contract at substantially the same rate.

7. The method of making an electrical device that consists in disposingheated material around. a conductor simultaneously passing an electriccurrent thercthrough, and thereafter cooling the said conductor and thesaid material in such manner that they contract at substantially thesame rate.

8. The method of making an electricaldevice that consists in disposingmolten material around an insulated conductor simultaneously passing anelectric current therethrough, and thereafter cooling the said conductorand the said material in such manner that they contract at substantiallythe same rate,

9. The method of making an electrical device that consists in casting anincasing member around a conductor, simultaneously passing an electriccurrent thercthrough, and varying the current as the member cools.

3.0. The method of making an electrical device that consists in castingan incasing member around a conductor and in good thermal contacttherewith. simultaneously passing an electric current through saidconductor, and reducing the current in accordance with the temperaturereduction of aid member as it cools,

11. The method of making an electrical device that consists in embeddinga conductor in insulating material, casting: an incasing member aroundsaid material, supplying an electric current to the conductor during thecasting operation, and varying the current as said member cools to causethe con ductor to contract at substantially the same rate as theincasing member.

12. The method of making an electrical device that consists insurroumlinc,- a conductor with relativclv plastic material of good heat-cond noting: properties. baking said. n'iaterial. casting; an incasion member around the combined body as a core. supplying a electriccurrent to said conductor during the casting operation and graduallyreducinf); the current value as the member cools W iercby saidconi'luctor. material and member contract at substantially the same rateand remain in mutual intimate thermal relation.

13. The method of making an electrical device that comprises heating anelectric conductor. surrounding the said conductor with heated material.and causin l the said conductor and the said material to cool sidevicethat comprises surrounding with In testimony whereof, I have hereuntoheated mziteyial a conductor that has been subscribed my name this 27thday of Dec. heated sufiielently to expand it to subst mn- .1913.

tially the same degree as the said matenal, A SAMUEL TRQOD. 5 andeausing the said conductor and the said Witnesses:

material to cool simultaneously and to con- B. B. Hume,

vact at sl'lbstantially the same rate. M. C. MERZ.

